Empire of Japan: minimum 1743 years to date (see above)
Byzantine Empire: 874 years (uninterrupted from 330 to 1204)
Holy Roman Empire: 844 years (962-1806)
Zhou Empire: 790 years (1046–256 BCE)
Ethiopian Empire: 666 years (1270-1936)
Khmer Empire: 629 years (802–1431)
I hope this helped :)
